1. Field of the Invention
The present invention generally relates to optical, gel-based devices that utilize the diffraction properties of crystalline colloidal arrays. More specifically, the present invention relates to polymerized crystalline colloidal array detectors whose diffraction wavelengths change in response to a variety of specific stimuli. These detectors have application in numerous chemical, environmental and medical technologies.
2. Background Art
Charged colloidal particles, when suspended in water, form a stable, crystalline dispersion due to interparticle coulomb repulsion forces. The property of structural ordering in such dispersions has been exploited in making devices such as narrow band optical rejection filters. The ordering phenomena in such colloidal suspensions have been useful in spectroscopy and Bragg diffraction techniques. It has been found that mesoscopic, crystalline structures can have many practical applications as optical filters in military, space, medical and research uses. In many such instances, it is necessary or desirable to filter narrow bands of selected wavelengths from a broader spectrum of incident radiation. Crystalline structures, or crystalline colloidal arrays (CCA), and their use in optical filtering devices are disclosed, for example, in U.S. Pat. Nos. 4,627,689 and 4,632,517.
Similar devices, in which a CCA is embedded in a polymer matrix, have also been disclosed. For example, U.S. Pat. Nos. 5,368,781 and 5,266,238 disclose tunable, narrow band radiation filters comprising a crystalline colloidal array of charged particles fixed in a hydrogel film. Methods for filtering incident radiation using these filters are also disclosed.
U.S. Pat. Nos. 5,330,685, 5,338,492 and 5,342,552 discuss narrow band radiation filters comprising a CCA of charged particles in a polymeric hydrogel. U.S. Pat. No. 5,281,370 also discloses a method of making a solid radiation filter material including one embodiment in which the particles in the array are fused together by polymerization.
Various sensor devices are also reported in the art. Schalkhammer, et al., disclose an optical sensor that utilizes the concept of pH-dependent swelling of special polymers. See Schalkhammer, et al., "The Use of Metal-island-coated pH Sensitive Swelling Polymers for Biosensor Applications", Sensors and Actuators B, Vol. 24-25, pp. 166-172 (1995). Conductimetric sensor devices have been proposed based on the selective swelling of hydrogels in response to pH by Sheppard, "Design of a Conductimetric Microsensor Based on Reversibly Swelling Polymer Hydrogels", Transducers '91, 773-776 (1991) and Sheppard, et al., "Microfabricated Conductimetric pH Sensor", Sensors and Actuators B, Vol. 28, pp. 95-102 (1995). Finally, sensor devices based on the selective swelling of hydrogels in response to glucose have been proposed by McCurley, "An Optical Biosensor Using A Fluorescent, Swelling Sensing Element", Biosensors and Bioelectronics, Vol. 9, pp. 527-533 (1994) and Kikuchi, et al., "Glucose-Sensing Electrode Coated With Polymer Complex Gel Containing Phenylboronic Acid", Anal. Chem., Vol. 68, pp. 823-828 (1996).
None of the art, however, discloses a sensor device that utilizes crystalline colloidal array diffraction as a detection means, as disclosed herein.